- We make an recurrent appointment in Outlook
- Synchronize the mobile with syncml
- Everything looks fine in the mobile
- Now we change the appointment NOT the serie but just one item
- Synchronize the mobile with syncml
- Now we see in the mobile that the appointments time has been changed always to 01:00
- We synchronize the mobile again with syncml
- Now the appointment is gone in Outlook!!!

As recurrence events are heavily tested with several sync servers and your scenario looks like a simple case, I have some doubts for the server.
It's known that the MDaemon server has some problems with VCALENDAR formats, see also our FAQ.

Nevertheless I'd like to help and look at a logfile with this scenario.
So please create again a recurrence event and sync it to the mobile.
Then change one occurence, as you've done already.

To sync with logs, just long click to the sync button and take the 2nd choice.
At the end let it send to the Synthesis server and keep me informed about sync time, URL, user name by email.